1. Field of the Invention
The present invention relates to a video coding/decoding buffering apparatus and a buffering method thereof, and more particularly, to a buffering apparatus using lower memory space and considering the real time characteristic of the video image in coding/decoding the new generation's video image, and a buffering method thereof.
2. Description of the Related Art
“Video coding” is a method for processing video data, wherein a new set of data is generated based on the original image data. The new set of data is called “compression result”. It is common that the size of compression result is much smaller than the size of the original image data, thus an image compression effect is provided. In addition, the compression result must be recoverable, that is the original image must be recoverable after performing an appropriate decoding process. Note that the compression result of the image is not an image any more, the real outlook of the original image can be obtained only after a decompression process. The conventional coding/decoding process generally comprises three major phases as follows:                (1) Dividing each video frame into a plurality of pixel macro blocks, such that the video frame can be processed in the macro block layer.        (2) Eliminating the spatial redundancies in the video frame by spatial estimation, or eliminating the temporal redundancies in the continuous frames by motion estimation or motion compensation.        (3) Coding the residual blocks remaining in the video frame, wherein the residual blocks are the difference between the original blocks and the estimated blocks; and the coding is performed by transforming, quantifying, and entropy coding techniques.        
In order to provide better video quality and coding efficiency, the new generation video coding/decoding technique generally adds a fourth step: using a filter to eliminate block effect generated in an encoding/decoding process of macro blocks.
Therefore, in order to perform the coding/decoding pipeline in the macro block level, the new generation's video coding/decoding apparatus has to reserve both of the unfiltered image and the filtered image.
In a conventional method, a whole set of unfiltered image has to be stored after the coding/decoding of all macro blocks are completed. Therefore, for a frame having M×N macro block, the size of information to be stored is about M×N×384 Bytes (GIF format: about 396*384 Bytes). Accordingly, a large size of memory space is required.
In another conventional method, a whole set of image is used as a pipeline level, and all information required for filtering of the whole set of image are reserved in the coding/decoding process. Therefore, such method has two disadvantages. First, all information associated to the macro blocks have to be reserved for further filtering process. Secondary, it is not possible to perform the coding/decoding pipeline in macro block level.